11/14/2012 08:27 am ET

Celebrities' Weight Loss Plans: Stars Who've Endorsed Diets (PHOTOS)

Nothing gives a weight-loss plan a boost like an endorsement from a boldface name like Jessica Simpson or Jennifer Hudson -- both of whom have recently used Weight Watchers to shed an impressive number of pounds.

Of course, even with the support of a big brand name, dieting is never easy. And some stars, such as Kirstie Alley and Carnie Wilson, have struggled to stay super-slim while under contract with a nutrition company.

The following celebrities have endorsed well-known weight-loss plans, with varying degrees of success.